Radioactivity of sand, groundwater and wild plants in northeast Sinai, Egypt

Conceptualization of arid region radioecology strategies for agricultural ecosystems of the United Arab Emirates (UAE)

Since the last decade, ambitious nuclear power programmes have begun maturing in the Arab countries, most importantly in the United Arab Emirates (UAE). The region's environment and population, therefore, are prone to adverse, long-term impacts of radionuclide discharges. To calculate the associated exposure scenarios, to estimate doses and their consequences, and finally, to lay out a radiological emergency management plan, arid region radioecology is taking shape in the UAE as a major field of research. Geography, demography, food habits, weather, soil, water, flora, and fauna of the desert-marine regions are quite distinct from their temperate counterparts. This results in the need to increase the knowhows of environmental migration and bioaccumulation of radionuclides in the region's agricultural ecosystems. In this paper, we present a detailed review of the measured data from the UAE and nearby nations, generating insights for the soil radioactivity and soil-to-plant transfer phenomena under local arid conditions. In the literature, the radionuclide activity concentrations (in Bq kg^-1) vary over five orders of magnitude depending on nuclide type, sample type, and locality. Variabilities over six orders of magnitude are observed for transfer parameters too, and in-depth studies on the transfer mechanisms are usually scarce. We discuss the recent progresses made in root and foliar uptake studies with methods relatively new to sandy soils, like controlled potting, and soil K_d measurements. Showing the serious gaps in the data and interpretations, we provide a justification for the immediate experimentation in the understudied aspects of radioecology in the UAE and in arid lands in general.

A critical review on the occurrence and distribution of the uranium- and thorium-decay nuclides and their effect on the quality of groundwater

This critical review presents the key factors that control the occurrence of natural elements from the uranium- and thorium-decay series, also known as naturally occurring radioactive materials (NORM), including uranium, radium, radon, lead, polonium, and their isotopes in groundwater resources. Given their toxicity and radiation, elevated levels of these nuclides in drinking water pose human health risks, and therefore understanding the occurrence, sources, and factors that control the mobilization of these nuclides from aquifer rocks is critical for better groundwater management and human health protection. The concentrations of these nuclides in groundwater are a function of the groundwater residence time relative to the decay rates of the nuclides, as well as the net balance between nuclides mobilization (dissolution, desorption, recoil) and retention (adsorption, precipitation). This paper explores the factors that control this balance, including the relationships between the elemental chemistry (e.g., solubility and speciation), lithological and hydrogeological factors, groundwater geochemistry (e.g., redox state, pH, ionic strength, ion-pairs availability), and their combined effects and interactions. The various chemical properties of each of the nuclides results in different likelihoods for co-occurrence. For example, the primordial ²³⁸U, ²²²Rn, and, in cases of high colloid concentrations also ²¹⁰Po, are all more likely to be found in oxic groundwater. In contrast, in reducing aquifers, Ra nuclides, ²¹⁰Pb, and in absence of high colloid concentrations, ²¹⁰Po, are more mobile and frequently occur in groundwater. In highly permeable sandstone aquifers that lack sufficient adsorption sites, Ra is often enriched, even in low salinity and oxic groundwater. This paper also highlights the isotope distributions, including those of relatively long-lived nuclides (²³⁸U/²³⁵U) with abundances that depend on geochemical conditions (e.g., fractionation induced from redox processes), as well as shorter-lived nuclides (²³⁴U/²³⁸U, ²²⁸Ra/²²⁶Ra, ²²⁴Ra/²²⁸Ra, ²¹⁰Pb/²²²Rn, ²¹⁰Po/²¹⁰Pb) that are strongly influenced by physical (recoil), lithological, and geochemical factors. Special attention is paid in evaluating the ability to use these isotope variations to elucidate the sources of these nuclides in groundwater, mechanisms of their mobilization from the rock matrix (e.g., recoil, ion-exchange), and retention into secondary mineral phases and ion-exchange sites.

AGE-DEPENDENT DOSE DUE TO INTAKE OF 40K, 228RA, 226RA IN SPRING WATER IN PETRA DISTRICT, JORDAN

A HpGe detector was used to measure radioactivity concentrations of 40K, 228Ra and 226Ra in spring water from villages in Petra district in southern Jordan. The concentrations of 40K, 228Ra, 226Ra were 0.64-2.72 Bq/l, 0.05-0.08 Bq/l and 0.15-0.22 Bq/l, respectively. These values were compared to the concentrations of the corresponding radionuclides in studies from Jordan and near countries. The annual effective doses (${D}_{\mathrm{eff}}$) due to the intake of 40K, 228Ra and 226Ra, for the different age groups were calculated. The highest ${D}_{\mathrm{eff}}$ values due to the intake of 226Ra and 228Ra were found in the infants age group, whereas the lowest were found in the adults age group in every site. The annual effective doses in this study were compared to the committed annual effective doses from ingestion in UNSCEAR. The annual effective doses in this study were much higher than the committed values in UNSCEAR. The life time risk for radiation-induced cancer for the whole population was calculated for every sample and it revealed no extra risk over the one recommended by WHO.

Effect of salinity on the concentrations of radioisotopes in the aquatic environment of a hypersaline coastal lagoon

Research of the effect of salinity on the fate of radionuclides has been focused on seas or estuarine systems while there is almost no information on marine environments with a salinity higher than that of sea water. The hypersaline Bardawil lagoon is a concentration basin, with evaporation exceeding precipitation. This study presents the characteristics of some environmental factors including salinity and their influence on the distribution of natural and artificial radionuclides in different compartments of the lagoon. The concentrations of (238)U, (234)Th, (228)Ra and (137)Cs in sediments show some degree of dependency on the water's salinity. Migration of these radionuclides in the lagoon's sediments must take place from high salinity to low-salinity regions. Cluster analysis revealed the data structure for sediment by separating (137)Cs and (40)K from (232)Th, (226)Ra, and (234)Th and for sand by separating (40)K from the other radioisotopes.

Environmental assessment of gamma-radiation levels in stream sediments around Sharm El-Sheikh, South Sinai, Egypt

A total surface area of ∼170 km(2) including 28 localities around Sharm El-Sheikh, South Sinai, were investigated by γ-ray spectroscopy. The concentrations of NORM were found to be five to seven-fold that in dune sands in different regions in Sinai. While relatively higher levels of (238)U, (234)Th, (226)Ra, and (232)Th are associated with the existing monzo-syenogranite, the concentration of (40)K is more uniformly distributed in the studied area. Locations with higher concentrations of (137)Cs are mainly located in the northern part. The (238)U, (234)Th and (226)Ra isotopes in the (238)U-series are in secular equilibrium. The absorbed dose rates and gamma-radiation hazard indices in all locations were higher than the world average value and unity, respectively. Properly regulated land use is recommended for a buffer zone in the northern part of the study area.

Evaluation of some pollutant levels in environmental samples collected from the area of the new campus of Taif University

The levels of radioactivity and heavy metals in soil, plant and groundwater samples collected from the area of the new campus of Taif University, Saudi Arabia, and its neighbouring areas have been determined. High-resolution gamma-ray spectroscopy was used for radioactivity measurements, and inductively coupled plasma atomic emission spectroscopy was used to determine the concentration of heavy metals. The means of (226)Ra, (228)Ra and (40)K concentrations in water samples collected from four wells were found to be 0.13 ± 0.03, 0.05 ± 0.03 and 1.3 ± 0.5 Bq l(-1), respectively. The means of (238)U, (226)Ra, (228)Ra ((232)Th for soil samples) and (40)K concentrations in wild plant and soil samples were found to be 3.7 ± 4.1, 8.8 ± 11.6, 3.8 ± 2.9 and 1025 ± 685, and 8.6 ± 3.4, 12.8 ± 3.4, 16.6 ± 7.1 and 618 ± 82 Bq kg(-1) dry weight (DW), respectively. The (137)Cs of artificial origin was also detected in soil samples with a mean concentration of 3.8 ± 2.2 Bq kg(-1) DW. Evaluating the results, it can be concluded that the concentrations of (238)U, (226)Ra, (232)Th and (40)K in soil samples fall within the world average. Furthermore, 19 trace and major elements in groundwater samples and 22 elements in soil and plant samples were determined. The sampling locations of soil can be classified into three groups (relatively high, medium and low polluted) according to their calculated metal pollution index using the contents of trace and major elements. A cluster analysis of the contents of radioactivity and trace element contents in soil samples shows the presence of two main distinct clusters of sampling locations.